A liquid crystal display device performs overshoot driving (also referred to as overdriving) in order to improve response speed of a liquid crystal panel. The overshoot driving is a driving method for applying, to liquid crystals, a voltage corresponding to a gradation higher than a target gradation when increasing display gradation, and applying, to liquid crystals, a voltage corresponding to a gradation lower than the target gradation when decreasing the display gradation. By performing the overshoot driving, it is possible to increase movement speed of liquid crystal molecules, and to improve the response speed.
A liquid crystal display device performing the overshoot driving has a problem that when displaying a specific color, a lateral electric field occurs between two sub-pixels that are adjacent to each other and the response speed of the liquid crystal panel decreases. This problem will be described with reference to FIGS. 11 and 12. FIGS. 11 and 12 show sections of a liquid crystal panel. The liquid crystal panel is configured such that a liquid crystal layer 92 is sandwiched between two glass substrates 91a and 91b. The glass substrate 91a is provided with thin-film transistors (not depicted), a pixel electrode 93, and the like, and the glass substrate 91b is provided with an opposite electrode 94, a color filter 95, and the like. Each of color pixels included in the liquid crystal panel is constituted by three sub-pixels 96r, 96g, and 96b. 
The liquid crystal panel illustrated in FIGS. 11 and 12 is assumed to be of a normally-black type. When performing white display after black display, a high voltage VM corresponding to a maximum gradation is applied to the liquid crystal layer 92 for any of the three sub-pixels 96r, 96g, and 96b (see FIG. 11). By contrast, when performing green display after black display, while the same voltage VM applied in the white display is applied to the liquid crystal layer 92 for the sub-pixel 96g, voltages applied to the liquid crystal layer 92 for the sub-pixels 96r and 96b remain substantially zero (see FIG. 12). At this time, lateral electric fields 90 occur between the sub-pixels 96r and 96g, and between the sub-pixels 96g and 96b. 
When the lateral electric field 90 occurs, a part of the liquid crystal molecules (not depicted) within the liquid crystal layer 92 are inclined in horizontal direction, instead of vertical direction. If the orientation of the liquid crystal molecules is disturbed in this manner, the response speed of the liquid crystal panel decreases. In FIG. 12, the higher the voltage VM is, the stronger the lateral electric fields 90 become and the more easily the response speed decreases. Furthermore, the larger a gradation difference between the two sub-pixels that are adjacent to each other is, the more easily the response speed decreases. For example, in a case of the normally-black type liquid crystal panel employing an RGB method, the response speed is noticeably decreased when displaying red, green, blue, or a color close to any of these colors.
As a method for solving this problem, there has conventionally been known a method of making an overshoot gradation lower than that originally is when display gradation changes from a value around a minimum value to a value around a maximum value, when performing overshoot driving to a normally-black type liquid crystal panel. For example, when performing 256-level gradation display, the overshoot gradation when display gradation changes from 0 to 255 is set to be 240, instead of 255. According to this method, even in the case shown in FIG. 12, by decreasing the voltage VM applied to the liquid crystal layer 92 for the sub-pixel 96g, it is possible to suppress the lateral electric fields 90 and to improve the response speed.
Relating to the present invention, it should be noted that Patent Document 1 describes a liquid crystal display device that, when brightness of an image frame changes in an order of a low brightness gradation, the low brightness gradation, and then a middle brightness gradation, replaces the middle brightness gradation with an overshoot gradation that is higher than the middle brightness gradation, and replaces the low brightness gradation immediately before the middle brightness gradation with a gradation for pretilt that is higher than the low brightness gradation, in order to improve video display performance.